NONE AT THE MOMENT, SORRY.....

Pluto, the Roman God of the Underworld, was only discovered in 1930 by Clyde Tombaugh.  Actually, it's considered by many (including me) not to be a proper planet, merely a large 'cosmic iceberg' captured by the Sun.  For the sake of argument though, and because in most textbooks it is considered to be a planet, I'll refer to it as a planet.   Therefore, it's the smallest, farthest and coldest 'planet' orbiting the Sun.   Its diameter is just 2,320 kilometers (about two thirds that of our moon) and it has a very epilleptical orbit.  Suprisingly enough though, Pluto has a moon of its own; Charon.  Charon is 1,210 kilometers wide, more than half the diameter of Pluto itself!  Becuse of this, Pluto is what's called a 'Double Planet'.  Pluto has a rather strange orbit because although it's usually the farthest planet from the Sun, there is an occasion during its orbit that it's actually inside Naptune's orbit!   This last happened in 1979 and because of this, Neptune's distance from the Sun varies wildly.  At the moment it's quite close though.  Pluto also has a thin atmosphere of Carbon Dioxide and Methane.  This atmosphere is not permanent though and when Pluto gets too far from the Sun, it collapses.  This is next expected to happen in 2010.

As you may have guessed, not too much is known about Pluto because a) it's so far from Earth's telescopes and b) no spaceprobe has ever visited it.   While point a) can't be helped, point b) can be, and probably will be.  The Pluto-Kuiper Express is a reconnaissance probe which is planned for a 2004 launch date.   It would visit both Pluto and Charon closely and then perhaps go on to the Kuiper ice-planets.  If everything goes according to schedule, it should be launched in 2004 and would arrive in about 2010, hopefully before the atmospheric collapse.

Pluto was discovered in 1930 by american astronomer Clyde Tombaugh and its moon Charon was discovered in 1978 by american astronomers James Christy and Robert Harrington.